Metrics vs inch Q

[brandett]

Which snap on size should i order to use for removal of a broken head stud ??

I can't find the same type of tool in Sweden so I will ask my brother to pick this up and send it to me.

I think i should order 3/16" but i really want to make sure. The head stud bolts are M10 (yeah metric...) and i figured that the 3/16 is closest to the recommendation as they should be used for 3/8 bolts.

If it wasnt for the weigth i would have ordered the kit, but i want it to be sent in an envelope.